A well-recognized problem with regard to flosses, whether they are tape flosses or multifilament flosses, is the catching on tooth surfaces during movement into and through close contact interdental spaces. In some instances the floss will break and shred and parts of the floss will become stuck between the teeth. It then takes more flossing to remove floss segments from between one's teeth. This has been a continuing problem which is solved through the use of the new polytetrafluoroethylene (PTFE) fiber flosses. However, PTFE is a relatively expensive fiber. Therefore, it has been an objective to provide a fiber that has the ease of use characteristics of PTFE while using a lower cost fiber. This can be the result of forming a particular fiber composition or it can be by providing a coating on a non-PTFE fiber that makes the non-PTFE fiber mimic a PTFE fiber in use as a floss. Since a PTFE fiber has a low coefficient of friction (COF), it inherently readily passes into close interdental spaces.
PTFE flosses are disclosed in U.S. Pat. Nos. 5,033,488 and 5,209,251. These consist of one or more strands of expanded PTFE with a wax or other coating to increase the grippability of the fiber in use as a floss. A microcrystalline wax was found to be one effective wax. However, other coatings that adhere to PTFE, that are not brittle at about room temperature and which have a melting point above 50.degree. C. can be used. The coating will raise the COF of the expanded PTFE above about 0.08. A wax coated non-PTFE fiber floss is disclosed in U.S. Pat. No. 4,996,056. In this patent there is disclosed a nylon, polyester or polypropylene fiber that is coated with solid particles of a fluoropolymer in a binder. The binder can be a wax or a non-wax, with a wax being preferred. The fluoropolymer particles can be PTFE particles of a particle size of about 1 to 50 millimicrons. European Patent Application 423 541 A2 discloses formulations for coating flavorants and other materials onto PTFE surfaces, including flosses.
These patent publications set out the present state of the art of flosses that contain PTFE. The expanded PTFE fiber flosses slip easily into tight interdental spaces. However, expanded PTFE film can cost 3 to 10 times the cost of other fibers. Although a useful floss fiber, it is expensive. The non-PTFE fiber coated with particulate PTFE is not a low COF floss. This is the case since the PTFE particle coating is scrapped from the fiber during insertion between the teeth and the subsequent motion of the floss. The full benefits of a PTFE fiber then are no longer achieved.
Waxes have been coated onto conventional floss fibers for many years. Although microcrystalne waxes are the most commonly used waxes, other waxes, such as beeswax, paraffin waxes, carnauba wax and polyethylene wax can also be used. The floss fibers are usually nylon, however, other fibers such as polyethylene, polypropylene, polyester, cellulose and cotton also are used. The wax coating lubricates the fiber so that it can more easily slip into tight interdental spaces and also serves as a binder for multifilament flosses. However, none of these coatings onto these floss fibers have proven to impart to the non-PTFE fibers the characteristics of PTFE flosses. The objective is to use a lower cost conventional fiber and to achieve the surface lubricity of PTFE.